Electric wave translating system



July 13, 1937. s. E. ANDERSON 2,086,595

ELECTRIC WAVE TRANSLATING SYSTEM Filed July 8, 1924 2 Sheets-Sheet l July 13, 1937. s E ANDERSON 2,086,595

ELECTRIC WAVE TRANSLATING SYSTEM Filed July 8, 1924 2 Sheets-Sheet 2 VOLTAG E' AMPUFICATION Y wAvs LENGTH- Memes .gf my Patented July 13, 1937 UNITED STATES PATENT OFFICE ELECTRIC WAVE TRANSLATING SYSTEM Application July 8, 1924, Serial No. 724,762

35 Claims.

This invention relates to electric wave signaling systems, and more particularly, to means for eliminating the effects of undesired energy variations in such systems.

In carrier wave signaling systems, and particularly in radio systems employing space discharge tubes, designed to transmit .or receive speech or music, numerous attemptshave been made to utilize sources of alternating current for sup1 l plying space current, filament heating current and also polarizing potentials to the control elec= trodes of the tubes of the system. Heretofore, all such attempts have resulted to a greater or lesser degree in the introduction of undesired potential variations into the system tending to adversely affect its stability and also the quality and volume of received signals.

The use of alternating current in radio sys tems for the purposes described, however, has 2o, important advantages in that the circuits maybe simplified, the eiiiciency of operation may be in creased, and the cost of construction and opera tion reduced to a minimum. v:Batteries forhsupplying current may be eliminated and ordinary 110 or other voltage alternating current used to supply the system.

An object of this invention is to eliminate disu turbing effects in radiant energy or other electric wave signaling systems utilizing alternating current sources.

Another object is to prevent the introduction of ripples tending to distort the signals in systems utilizing sources of alternating current.

An additional object is to maintain a uniform potential over` the surface of the cathodes of space discharge tubes included in an electric wave sig= naling system.

4A further object is to prevent current flowing in the heating element of space discharge tubes having equipotential cathodes from introducing variations in the potential gradient between the cathodes and anodes of the tube.

Another object is to compensate for inherent leakage between different portions of the apparatus of a radiant energy signaling system, thereby CII 4 preventing the introduction into the system of,

undesired energy variations which tend to in= terfere with the signals.

A feature of the invention relates to an ar= rangement whereby energizing currents and control potentials may be supplied by a single al ternating current source to space discharge tubes included in an electric Wave signaling system, in such manner that variations of the energy supplied by the source do not cause interference with the signals.

Another feature relates to a signaling system utilizing space discharge tubes, including electron emitting cathodes having means connected 5 between the cathodes and heating elements theren for which maintains a substantially uniform potential over the surfaces of the cathodes.

Another feature relates to a grid lter arranged to prevent variations of current in the output l0 circuit of space discharge tubes from affecting the potential applied to the control electrodes of the tubes.

Broadly, this invention comprises an electric Wave translating system utilizing space discharge l5 tubes having cathodes of large surface area which are arranged to be heated by radiation from a heating element such as an incandescent lilament.

The system utilizing these tubes, known as equipotential cathode tubes, is arranged to be supplied with energy from a single source of alternating current. The heating elements or filaments of the tubes may be supplied with current from a transformer having its primary winding connected to the source of alternating current. Space current for the tubes is supplied from the source of alternating current through a rectier and filters. Potential for the control electrodes is provided by the drop of potential along a resistance common to the input and output circuit of the tubes. Filters are included in the circuit for connecting this resistance to the control electrodes of certain tubes of the system to prevent variations of voltage drop across the resistance from being transmitted to the control electrodes. y

In order to prevent changes in the drop of potential along the heating element or lament of the tubes from introducing changes in the poten- 4g tial gradient between the cathodes and anodes of the tubes and from producing inequalities in the distribution of potential over the surface of the cathodes, or from producing other ell'ects which would cause variations in the space current flowing through the tubes, a path having low impedance for alternating currents and high impedance for direct currents is provided between the cathodesnd iilaments of the tubes. This path in one instance may be provided by series condensers having their terminals connected to opposite sides of the lament heating circuit and their mid-point connected to the cathodes. In another instance, the path may be provided by a condenser having one plate connected to the cathodes and its other plate connected to the mid-point of the secondary winding of a transformer supplying current to the heating fila ments. This path seems to balance the circuit of the system so that changes in the drop of potential along one-half of the heating filaments are exactly compensated by the changes in the drop of potential along the other half of the filaments. By virtue of this arrangement these changes do not produce, either directly or indirectly, changes in the space current flowing through the tubes and consequently do not detrimentally effect the signals received.

The invention both as to its organization and method of operation to effect the objects noted above, as well as the additional features and objects, will be better understood by reference to the following detailed description taken in connection with the drawings in which:

Fig. 1 illustrates a radio receiving system employing equipotential cathode tubes supplied With energy from a source of alternating current.

Fig. 2 illustrates a slightly different method of connecting the cathodes and heating filaments for preventing ripples in the space current of the tube.

Fig. 3 illustrates one form of the space discharge tubes of Fig. l.

Fig. 3a is a view in section of the tube electrodes taken on line 3a-3a of Fig. 3.

Fig. 4 illustrates a form of space discharge tube different from that shown in Fig. 3.

Fig. 5 is a transparent perspective view partly in section illustrating a transformer of the systern of Fig. 1.

Fig. 6 shows a characteristic curve illustrating the properties of the transformer.

The circuit illustrated in Fig. l includes an antenna I0 coupled to high frequency amplifier 20 arranged in tandem with a detector 30 and a low frequency amplifier 40. The amplifier 40 supplies signal currents to a cone type loud speaking receiver 50.

The antenna circuit includes a variable condenser II in series with a loading coil I2 and the primary winding of a variable transformer I3 having one terminal connected to ground. The secondary winding of transformer I3 has one terminal connected to the grid of space discharge tube 2| and the opposite terminal connected to the anode of this tube in series with a small adjustable condenser I4. A variable condenser I5 is connected in shunt across the secondary winding to form a resonant circuit therelwith. 'I'he resonant circuit may be tuned by adjusting this condenser. The antenna circuit may be tuned by adjusting condenser II.

The tube 2| includes in addition to the grid and anode already mentioned, a cathode 22 and a filament 23.

The input circuit for the tube is connected between the grid and cathode and may be traced as follows: from the grid of the tube, one-half of the secondary winding of transformer I3, the mid-tap of this winding to the grid filter resistance 25 to the cathode 22 and across the space Within the tube to the grid.

The alternating current output circuit for tube 2| is connected to the cathode and anode. This circuit may be traced from the anode to primary winding of transformer 26, by-pass condenser 2'I to the cathode 22 and across the space within the tube to the anode. A space current circuit for tube 2| is also connected toits anode and cathode and may be traced from the anode, through primary winding of transformer 25, niter 28, secondary windings 3| and 3l' of transformer 32, rectifier 25, resistance 25 to the cathode 22.

The resistance 25 is included in a portion common to both the input circuit of tube 2| and its space current circuit.

The secondary winding of transformer 26 is included in the input circuit of the space discharge tube 36 in series with a blocking condenser 34 shunted by a leak resistance 35. This input circuit is connected to the control electrode and the cathode of tube 35.

The output circuit of tube 3B is connected to the anode and cathode of the tube and includes the primary winding of low frequency transformer 31 in series with by-pass condenser 33 both shunted by a second condenser 39.

The space current path of the tube 36 may be traced fromthe anode to the primary winding of the transformer 31, filter 4I filter 23, secondary windings 30 and 3l of transformer 32, rectier 29, resistance 25 to the cathode of the tube.

The secondary winding of the transformer 31 is included in the input circuit of a low frequency amplifier 4I). This input circuit may be traced from the grid of tube 42, secondary winding of transformer 31, filter 43, resistance 25 to the cathode of the tube 42. The alternating current output circuit of tube 42 extends from the anode through the primary winding of transformer 45 and by-Dass condenser 2l to the cathode.

The space current circuit of tube 42 extends from the anode of the tube through the primary winding of transformer 45, filter 28, windings 30 and 3l of transformer 32, rectifier 23, resistance 25 to the cathode of tube 42 and across its space path to the anode. The resistance 25 is included in the input and space current circuits of tube 42. 'I'he secondary winding of transformer 45 is connected to the loud speakingreceiver 50.

The cathodes of the tubes 2|, 36 and 42 are ccnrected to a common lead extending to ground a The tubes 2|, 36 and 42 comprise heating elements or filaments 23, 41 and 43 respectively, which are connected in parallel to a secondary winding 33 of transformer 32. The primary winding 43 of this transformer is shown connected to a source of alternating current. This represents any desired source of current and may be an ordinary house lighting circuit supplying sixty cycle current at commercial voltages. In this case the terminals of the primary winding of transformer 32 would be connected to a terminal plug adapted to cooperate with the particular type of outlet socket available. Condensers 5I and 52 are connected in series with each other and in shunt to the filaments of the tubes. The adjacent plates of these condensers are connected by lead 53 to the cathodes of the tubes.

The path between the cathodes and filaments of the tubes including the condensers 5I and 52 is provided to prevent the alternating current owing in the heating filaments of the tubes from introducing ripples in the space current supplied to the tubes which would tend to cause interference with signals.

The filter 24 comprises a shunt capacity element 24. and a series resistance element 24a. Filter 43 comprises a shunt capacity element 43' and a series resistance element 43a. Resistance 25, is shunted by a condenser 25' which provides a low impedance path in parallel to the resistance for alternating current components. The filter 24 is arranged to prevent any residue of the variable current component ilowing in resistance 25 from producing variations in the potential applied to the grid oi tube 2|. Filter 43 serves a similar purpose with respect to potentials applied to the grid of tube 42.

The small condenser I4 is provided to compensate for the inherent capacity between the grid and anode of tube 2| to thereby prevent the production o1' parasitic oscillations caused by the transfer of energy from the output circuit ofthe tube to its input circuit through the tube capacity. The proper degree of compensation may be secured by adjustment of condenser I4. An advantage obtained by the use of this condenser is that of increased amplifying power without causing singing in the tube circuits or distortion of signals.

Suitable average polarizing potentials are supplied to the grids of tubes 2| and 42 by the drop oi potential caused by the flow of space current through resistance 25.

A suitable average potential is obtained for and impressed upon the grid of tube 36 by the wellm known action of the blocking condenser 34 shunted by the leak resistance 35.

Condensers 21 and 38 provide low impedance paths for alternating current associated with the tubes 2l and 36, respectively. They are in shunt to the source supplying space current thereto. The condenser=39 provides a low impedance path about the primary winding of low frequency transformer 31 for any high frequency current component present in the output circuit of tube 36.

In Fig. 2 there is illustrated a connection ben tween the filaments and cathodes of the space discharge tubes of the system which may be sub= stituted for that shown in Fig. 1. This connection provides a low impedance path for alters nating current of the frequency of the energizing source. in this arrangement the lead 53, con necting the mid-point of the secondary winding 33 of transformer 32 to the electron emitting cathodes of the tubes, includes a condenser 51a. This connection may be incorporated into the circuit of Fig. 1 by substituting the corresponding elements of Fig. 2 therein and by omitting the condensers 5I and 52 of Fig. 1.

The construction of the tubes 2 I, 36 and 42 used in Fig. 1 is illustrated in detail in Figs. 3, 3a and 4.

As illustrated in Fig. 3 and more clearly shown f in Fig. 3a the tube structurecomprises a plurality of electrodes including an anode 60, a control electrode 6l, an electron emitting cathode 62 and ilament or heating element 63 as already enumn erated. The relative positions of these elements will be understood by reference to Fig. 3a which is a view in section on line 3a,-3a. of Fig. 3.

The various electrodes of the tube are insulated from each other and supported by individual members 64, 65, 66 and 61 which are in turn sup-s ported by the standards 68 and 69 extending ver1 tically from the stem 10.

The stem and standards are constructed of insulating material preferably of glass and made integral with each other and with the envelope or bulb 1I. The bulb completely encloses the elecn Atrodes and the standards 6.8 and 69, and is exhausted to a high degree.

'I'he anode, control electrode, electron emitting cathode and filament are provided with lead-in conductors 12, 13, 14 and 15, respectively, which pass through the lower wall of the envelope 1i,

or through the stem 1l. The'ends oi! these conductors are attached to external terminals 16, mounted on the base oi the tube. This base includes an insulating disc 11 held in position by a cylindrical collar 16. The base is attached to the bulb 1l in the usual manner.

The tube is adapted to t into a tube 'socket having contacts with which the terminals 16 respectively engage. I

A getter 19, supported by standard 69 extends above the electrodes of the tube within the envelope 'Il and terminates in a circular ring 80 having a narrow ribbon of magnesium wound thereon.

In Fig. 4 there is shown a tube structure which diii'ers from that illustrated in Fig. 3. In this construction the standards comprise vertical wires 66 and 69' having their lower ends sealed in the stem 10 of the tube.

The upper ends of the wires 68 and 63' are attached to and support a bridge 8| of insulating material by which in turn the grid 6|, the electron emitting cathode 62 and heating illament 63 are supported and insulated from each other.

The anode or plate 66 is heldin position by horn izontal Wires B attached to the standard 66 and 69. The lower end of the' standard 68 passes through the stern 10 and serves as a lead-in conductor for the anode. The getter 19 is attached to the upper end of the standard 68. in other respects the arrangement of this tube is similar to that of Figs. E and 3a.

The electron emitting cathode 62 consists of a cylinder of nickel coated on its outer surface with `is as follows: When signal modulated waves are received by antenna I0, which may be tuned to the frequency thereof by adjusting condenser l 1 corresponding oscillatory currents are established in the resonant circuit formed by the secondary winding of transformer I3 in cooperation with the condenser i5, it being assumed that this circuit is tuned to the frequency of received waves.

The amplifier 26 operates to produce in its output circuit, ampliiied currents which correspond in frequency to the waves received by antenna I0. These currents ilow through the primary winding of transformer 26 to produce corresponding potential variations in the secondary winding and these are supplied to the grid of tube 36.

By virtue of the well-known action of detector 36, demodulation occurs and currents of signal frequency are produced in the output circuit of this tube. These currents iiow through the primary windingA oi transformer 31 and induce corresponding potentials in its secondary winding which are supplied to the control electrode of tube 42.

'I'he low frequency signal waves are ampliiied by tube 42 in a manner now well understood and supplied through transformer 45 to the loud speaking receiver 5U. The diaphragm of this receiver being vibrated in accordance with the signal currents supplied to it produces sound waves corresponding to the signals.

By virtue of the large surface of the cathodes of tubes 2i, 36 and 42 the internal impedance oi the tubes is made so small that the emciency thereof as amplifiers is greatly increased. Because of this fact the number of tubes required for a given degree of ampllllcation is greatly reduced.

As has already been explained a balanced path between the electron emitting cathodes and heating filaments of the tubes is provided by condensers and 52. This path prevents variations corresponding to the frequency of the source of alternating current connected to the primary winding of transformer 32 from affecting the space current iiowing through the tube. A new result is thereby produced, in that alternating current may be utilized and the attendantv advantages gained while at the same time ripples are eliminated from the system. This may be explained by the fact that any change in the potential gradient, between the cathodes and anodes of the tubes which is produced by a change in the drop of potential along one-half of each filament, will be opposed by asimilar change, simultaneously produced by variations in the drop of potential along the other half of each filament, whereby their effects will be neutralized.

The construction of the radio frequency transformer and its operation in the circuit described above to secure uniformity of transmission over a wide range of wave lengths will now be described'.

Referring to Fig. 5 the transformer windings |06, |0'| and |08 are illustrated partly in section to show the manner of winding. These coils are disc-shaped and have an inner and outer diameter and a depth of winding, all of which are large compared with the width of the winding. In practice these dimensions may be conveniently determined by accurately cutting grooves having these dimensions into a block or spool of suitable material, such as hard rubber or wood, and winding the coils in the grooves. The outline of this spool is indicated at |09.

It has been found that when coils are wound in this manner, are coaxially arranged in parallel planes, are constructed with dimensions included within certain limits and with the proper circuit connections, the transmission characteristic of a receiving set, such as shown in Fig. 1, will in general be represented by the well-known double humped curve of coupled circuits.

It has been found that, as the dimensions of these transformer windings and their separation are varied, the transmission characteristic of the set varies markedly. It has also been found that, as the two coils are brought nearer to each other, the two humps of the characteristic are separated further apart. l

Referring to Fig. 6 the curve a--c represents a measured characteristic plotted, between the wave length and voltage amplification of a twowinding coil. :For example such as the coil |01|08 when it is connected into the circuit in the manner in which it is used in Fig. 1, but without having associated with it the extra winding |06.

When the extra winding |06, which is opencircuited and not connected to any portion of the circuit, is associated with the windings |01 and |08, a suitable dimension of the coils and a suitable spacing between them being observed, the characteristic of the transformer as a whole is changed from the characteristic curve ac to the curve ab.

As a result of measuring a large number of two-windings radio frequency transformers, it

has been observed that there is a marked tendency for the peak of the characteristic occurring at the longer wavelengths to be much more pronounced than the peak occurring at the shorter wave lengths. But by employing an extra winding, such as |06, in connection with the windings that are -connected into the circuit. the transmission may be greatly reduced in the region of the long wave length peak as is indicated by the curve a-b.

It will be observed by comparing the curve that the `effect of the extra winding is not only to prevent the amplification rising to such a high value in the long wave length region, but it also operates to raise the amplification at each side of the peak portion by producing two minor peaks which are spread over a greater wave length range than the single prominent peak of the characteristic a-c. As a result, a characteristic a-b is obtained which not only gives a more uniform transmission than the curve af-c but also gives high transmission for longer wave 'lengths than in the case of the characteristic a-c.

The coils of the transformer preferably should have an internal diameter of one inch or greater, a winding depth of the order of one-half inch or more, a width of winding at least as small as one-eighth of the depth of the winding, and a separation between the windings of the order 0f one-quarter of an inch or less. These dimensions may be varied considerably from the values here given so long as the relative proportions stated are approximately adhered to. Each winding has a terminal connected to its inner layer and a terminal connected to the outer layer. In connecting this coil into the circuit, either the inner layer of the primary is connected to the plate of the tube 2| and the outer layer of the secondary is connected to the grid of the tube 36 (the other terminals being connected through the necessary apparatus or other filaments to the filament circuit), or the outer primary terminal is connected to the plate and the inner secondary terminal is connected to the grid.

As an illustration of the dimensions of the transformers which have proved advantageous in a particular case, it may be stated by way of example, that in the particular case the transformer consisted of two similar windings each having an inner diameter of one and one-quarter inches, a width of winding of three-sixty fourths of an inch and a spacing between the primary and secondary winding of one-eighth of an inch. Each of the connected windings comprising 200 turns of No. 36 Brown and Sharpe gauge double silk-covered copper wire, and an extra open-circuited winding comprising 430 turns of the samesized wire wound in a groove of the same diameter, and three-thirty seconds of an inch wide, and spaced one inch from the primary transformer winding.

Fr'om the preceding description it will be apparent that the present invention provides an electric wave signaling system in which signals may be faithfully reproduced with exceptionally great volume. This is effected, in part. by using space discharge tubes including equipotential cathodes for high frequency amplification, detection and low frequency amplification and an alternating current source for. supplying heating current to the cathode heaters and space current to the tubes, as well as polarizing potentials to the control electrodes of amplifiers, with the source so connected that distortion of and interference with the signals is prevented.

The overall eiciency and flexibility oi the system is materially increased by using a high frequency transformer having a high transmission efficiency over a relatively broad range .of

5 frequencies or wave lengths. Another contribution to the efdciency of the system is obtained by using tubes of simple and rugged-construction-` possessing relatively great electron emissivity.

A further advantage of the system resides in the fact that the number of tubes required to operate loud speaking devices is reduced to a minimum and, in the fact that, by using the ordinary commercial house lighting system as a supply source for' the tubes, the use of expensive batteries ordinarily required is avoided. Thus a compact and emcient vloud speaking system, which is especially economical as to rst cost and cost of operation, is provided.

Although the invention has been illustrated and described'in connection with certain specic embodiments, it is intended-to be limited only by the scope of the appended claims. What is claimed is:

1. In a radiant energy signaling systema plurality of space discharge tubes, said tubes each having an anode, cathode, control electrode and cathode heating element, input circuits connected to said cathodes and control electrodes, output circuits connectedto said cathodes and anodes, and means for supplying from a common source of alternating current, suitable average potentials for said control electrodes, space current for said output circuits and heating current to said heating elements, said lmeans including capacitive reactance in the heating current path for preventing variations in said source from affecting the flow of current in said output circuits.

2. In a radio receiving system, a plurality of space discharge tubes coupled in tandem, saidv tubes having a plurality of electrodes including a cathode and a filament, said cathode having a uniform potential, av source of alternating current for heating said filaments and means comprising a pair of series condensers connected in shunt to said iilaments, and a connection between said cathode and the mid-point of said condensers for preventing said source from introducing variations in the potential along said cathode.

3. In aradio receiving system, a plurality of space discharge tubes coupled in tandem, said tubes each having a plurality of electrodes including a cathode and a illament, said cathode having a uniform4 potential over its surface, a single source of alternatingcurrent supplying i5 energy to said tubes including heating current to said lament, and means including capacitively vreactive path connected in shunt to said illaments and a connection from the mid-point of said path to said cathodes for preventing variations of current from said source from changing the distribution of potential over the surfaces of said cathodes.

4. In a radio receiving system, a plurality of space discharge tubes coupled in tandem, said 05 tubes each having a plurality of electrodes including a cathode and a filament, said cathode having a uniform potential over its surface, a single source of alternating current supplying energy to said tubes including heating current to said filament. and means including series condensers connected to said cathodes and filaments for preventing variations of current from said source from changing the distribution of potential over the surface of said cathodes.

5. In a radio receiving system comprising a variations in said voltages. l0 l i' 6. In a radio receiving system, a source of alternating current, a rectifier connected tosaid. source, a plurality of space discharge tubes in cascade connection supplied with current froin said rectier, each tube comprising a cathode, 15 anode, control electrode and filament, means traversed by current'from said rectifier for applying a potential to said control electrodes, and means comprising frequency selective networks individual to said tubes for preventing variations` '20 in the current suppliedby said rectiiier from causing variations in said potential, each oi said networks comprising a shunt arm and a series arm.

7. The combination with an electric space dis- 25" charge tube having therein an anode, a cathode, a lament for heating said cathode, and a control element, of means for supplying energy to said tube, comprising an alternating current source, a rectifier, a transformer for coupling said 3G Y f source to said tube, said transformer having a l winding for supplying current through said rectier to the space path of said tube and polarizing potential to its control electrode, a winding for supplying current to heat said filament, and a 3 reactance associated with said last mentioned Winding to preventvariations in said source from causing ripples in the space current.

8. A high frequency receiving system comprising a high frequency amplifier, a detector and a 4U low frequency amplifier, each of said three devices including a thermionic electrode and a plurality of spaced electrodes, a common heating circuit comprising means for heating said thermionic elec- J trodes, an alternating current source supplying 45 energizing potentials to said plurality of electrodes and to said means, and means comprising a condenser connecting said heating means to said thermionic electrodes, said heating circuit having no metallic electrical connection with any 50 of said electrodes. Y

9. In a radio receiving system, a high frequency space discharge tube amplifier, a space discharge tube detector adapted to detect. and amplify signal Waves delivered by saidhigh freo' quency amplifier, a low frequency space discharge tube amplifier fed from said detector, means for supplying, from a common source of alternating current, control Lelectrode biasing voltages to said ampliflersand all necessary heat- 60 ing currents and plate voltages to said amplifiers and said detector, and frequency selective networks individual to the control electrodes of said amplifiers for preventing said source from producing ripples in the control electrode biasing 65 voltages, each of said networks comprising a shunt arm and a series arm.

10. The combination with a space discharge vessel comprising an anode, a cathode and cathode heating means, of means for supplying alter-` 7 0 hating heating current to said heating means, means for supplying anode potential to said anode, and means external to said vessel for preventing the heating current in said heating means from causing variation of the average volt- 75 age between the cathode and the anode during a half cycle oi' said alternating current.

11. The combination with a space discharge vessel comprising an anode, a cathode, and cathode heating means, of means for supplying to said heating means heating Acurrent subject to variatiommeans for supplying anode potential to said anode, and means external to said vessel, for preventing increase occurring in the heating current in said heating means from causing variation of the average voltage between the anode and the cathode during said increase.

12. In a radiant energy signaling system, the combinatinn set forth in claim 1 in which the heating current source is equipped with a midpoint connection and in which the means including capacitive reactance in the heating current path comprises a condenser connected between the cathodes and the mid-point connection. l

13. In a signaling system a plurality oi' electronic relays connected together in cascade and comprising a high frequency ampliner, a detector and a low frequency amplifier, the low frequency amplliler relay having a grid and plate associated with its input and output circuits; a source of rectified alternating current for energizing said high frequency amplifiers and said output circuit, filter means for minimizing iluctuations in the current supplied from said source, said illter means including reactive elements, an impedance having resistance and capacity in series and a separate resistance in shunt with the negative lead from said source between some of the filter elements and said source, and a connection between said input circuit and the end of said impedance adjacent said source whereby the grid of said low frequency ampliiier is rendered negative.

14. In combination, a themiionic device comprising an anode, an electron emitter and a control element, heating means associated with, but spaced from, said electron emitter, a transformer connected to said heating means, an impedance connected to a point on said transformer, the average potential of said point being constant with reference to the terminals of said transformer and means for connecting said electron emitter to said impedance.

15. In a vacuum tube circuit, the combination of a tubular plate, a tubular grid within .said plate, a cathode within said grid, a resistance element insulatingly mounted Within said cathode for heating said cathode, a transformer comprising a primary coil adapted to be arranged in series witha source of alternating current and a secondary coil, said secondary coil being in series with said resistance element, and an electrical conductor capable of transmitting electrical variations joining substantially the midpoint of said secondary coil to said cathode.

' 16. In a vacuum tube circuit, the combination of a tubular plate, a tubular grid within said plate, a cathode within said grid, a resistance element extending into said cathode but insulated therefrom for heating said cathode, a transformer comprising a primary coil adapted to be arranged in series with a source oi' alternating current and a secondary coil, said secondary coil being in series with lsaid resistance element, an electrical conductor capable of passing variable currents joining substantially the mid-point of said secondary coil to said cathode, and means for grounding the said electrical conductor.

17. In a vacuum tube circuit, the combination of a tubular plate, a tubular grid within said plate, a tubular cathode within said grid, a resistance element out of electrical contact with said cathode but within said cathode for heating it, a transformer comprising a primary coil adapted to be arranged in series with a source oi alternating current and a secondary coil, said secondary coil being in series with said resistance element, and an electrical conductor of low impedance to variable currents joining substantially the mid-point of said secondary coil to one end of said cathode.

18. In a vacuum tube circuit, the combination of a tubular plate, a grid within said plate, a tubular cathode within said grid, a looped resistance element within said cathode but out of electrical engagement therewith for heating said cathode, a transformer comprising a primary coil adapted to be arranged in series with a source of alternating current and a secondary coil, said secondary coil being in series with s'aid resistance element, said source of alternating current tending to produce disturbing components in the plate circuit of said tube and an electrical conductor joining substantially the mid-point of said secondary coil to said cathode, said conductor being such as to transmit currents necessary to reduce the intensity of said disturbing components.

19. In a vacuum tube circuit, the combination oi' a plate, a grid within the plate, a tubular cathode extending into said grid, a resistance element out oi' electrical engagement with said cathode but extending therein to render said cathode electronically active, a transformer having its primary connected to a source of alternating current and its secondary connected in circuit with said resistance element, and circuit connections connecting said apparatus in a balanced circuit to balance out the disturbing etects of the current passing through said resistance element.

20. In a vacuum tube circuit, the combination of a plate, a grid within the plate, a tubular cathode extending into said grid, a resistance element out of electrical engagement with said cathode but extending therein to render said cathode electronically active, a transformer having its primary connected to a source of alternating current and its secondary connected in circuit with said resistance element, and circuit connections connecting said secondary and said tube elements in a balanced circuit to balance out the disturbing effects of the current passing through said resist- 'ance element.

21. In a vacuum tube circuit, the combination of a tubular electron emitter, a resistance element out of electrical engagement with said tubular electron emitter for rendering the same active, a transformer having a primary connected to a source of alternating current and a secondary connected to said resistance element, and circuit connections connecting said secondary and said electron emitter in a balanced circuit to render ineffective the inductive effect oi the alternating current passing through said resistance element.

22. In a vacuum tube circuit, the combination of a tubular plate, a grid within said plate, a tubular cathode within said grid, a looped resistance element out of electrical engagement with said cathode but within said cathode for heating said cathode, a source of varying heating current connected to said resistance element for supplydevice, a power supply means for said devices ining heating current thereto, and an electrical connection between said cathode and a portion of said source the average potential of which is constant with reference .to the terminals of said source.

23. In a vacuum tube circuit, the combination of a plate, a grid, a cathode, a resistance element out of electrical engagement with said cathode for heating said cathode, a transformer having a primary winding for connection to a source of alternating current and a secondary winding in series with said resistance element, and an electrical connection between said cathode and substantially the mid-point of said secondary winding.

24. In a vacuum tube circuit, the combination of a plate, a grid, a cathode, a resistance element out of electrical engagement with said cathode for heating said "cathode, a transformer having a primary winding for connection to a source of alternating current and a secondary winding in series with said resistance element, and an electrical connection of low impedance for waves of disturbing frequencies derived from said source between said cathode and substantially the midpoint of said secondary winding.

25. In a vacuum tube circuit, the combination of a plate, a grid, a cathode, a heater for said cathode, means for supplying varying current to said heater for heating said cathode, and an electrical connection between said cathode and a point on said means,.the average potential of which is substantially constant with reference to the terminals of said means.

26. A plurality of thermionic devices connected in cascade and having anodes and cathodes, a power supply means therefor including a source of alternating current, a rectier, and filtering means for the rectified current constructed to filter the anode current to one of said devices more effectively than the anode current to another of said devices.

27. A plurality of thermionic devices connected in cascade and having anodes and cathodes, one of said devices being connected Aand suitably energized to detect modulated high frequency carrier currents and another of said devices being more powerful and more powerfully energized than said first device and connected to amplify the currents of modulation detected by said first device, a power supply means for said devices including a source of alternating current, a rectier, and filtering means for the rectified current constructed to filter the anode current to said detecting device more effectively than the anode current to said amplifying device.

28. A plurality of thermionic devices connected in cascade and h aving anodes and cathodes, a power supply means therefor including a source of alternating current, a rectifier, and filteringmeans for the rectified current constructed to filter the anode current to one of said devices more effectively than the anode current to another of said devices, said filtering means being substantially free from current drain other than that required for the anode currents of the thermionicl devices of said cascade.

29. A plurality of thermionic devices connected in cascade and having anodes and cathodes, one of said devices being connected and suitably energized to detect modulated high frequency carrier currents and another of said devices being more powerful and more powerfully energized than said rst device and connected to amplify the currents of modulation detected by said rst other than that required for the anode currents of the thermionic devices of said cascade.

` 30. A radio receiver having an audio amplifier tube, an electric circuit and a source of electrical energy for energizing the anode thereof, said circuit comprising filtering condensers and inductances and an ohmic resistor in circuit with said inductances and disposed in the return side of said circuit, a connection at one end of said resistor for biasing the grid in said tube, a second resistor in said connection, a condenser connected to the second resistor, and to the filament circuit of said tube, and a ground connection between said second condenser and said filament circuit, said second condenser and last-named resistor forming a circuit to filter out alternating current oscillations from the connection between said resistors and the grid.

31. In a vacuum tube circuit, the combination of a tubular plate, a grid within said plate, a. tubular cathode within said grid, a looped resistance element within said cathode but out of electrical engagement therewith for heating said cathode, a transformer comprising a primary coil adapted to be arranged in series with a source of alternating current and a secondary coil, said secondary coil being in series with said resistance i element, and an electrical connection joining substantially the midpoint of said secondary coil to said cathode.l

32. In a vacuum tube circuit, the combination of a tubular plate, a tubular grid within said plate, a cathode within said grid, a resistance element insulatingly mounted within said cathode for heating said cathode, a transformer comprising a primary coil adapted to be arranged in series with alsource of alternating current and a secondary coil, said secondary coil being in series with said resistance element, and means for conducting the flow of disturbing currents, joining substantially the midpoint of said secondary coil to said cathode.

33. In a vacuum tube circuit, the combination of a tubular plate, a tubular grid within said plate, a cathode within said grid, a resistance element extending into said cathode but insulated therefrom for heating said cathode, a transformer comprising a primary coil adapted to be arranged in series with a source of alternating current and a secondary coil, said secondary coil being in series with said resistance element, a lead for variable currents joining substantially the mid-point of said secondary coil to saidv cathode, and means for grounding thelsaid lead.

34. In a vacuum tube circuit, the combination of a tubular plate, a tubular grid within said plate, a tubular cathode within said grid, a resist- Aance element out of electrical contact with said cathode but within said cathode for heating it, a transformer comprising a primary coil adapted to be connected to a source of alternating current and a secondary coil, said secondary coil being in series with said resistance element, and a connection for conducting current variations joining substantially the mid-point of said secondary coil to one end oi said cathode. l

35. In a vacuum tube circuit, the combination alternating current and a secondary coil. said secondary coil being in series with said resistance element, and means including a wire Joining substantially the mid-point of said secondary coil to said cathode.

SIDNEY E. ANDERSON. 

